Reversing Polarity -- Voodoo or Easy Tweak?

The correct term when talking about wiring speakers is polarity as stated in the original question, not phase.

Phase has to do with time, polarity has to do with whether a signal is going positive or negative. If a speaker is wired with the wrong polarity it will be going out when it should be going in, and vice versa. I have friend who claims he can tell when it is reversed because a vocalist will sound like they are gulping air instead of exhaling.

When 2 signals are out of phase it means that one or the other has been shifted in time, it occurs earlier or later in time than originaly produced. One example is a crossover network. They not only attenuate the signals outside their passband, they also phase shift them so they occur at a different time relative to those in the passband.

The fact that many manufacturers use the terms interchangeably adds to the confusion, just as Eldartford did in his post. In the first part where he is talking about wiring the speakers the correct term is polarity. In the second when he talks about the Buffy Sainte-Marie recording the correct term is phase. This deliberate phase shifting is the same thing Hendrix did to get that swirling effect with some of his recordings.

If ONE speaker has + and - (it's polarity) reversed, then the system will be "out of phase".

Their polarities are reversed, they are not out of phase. However, this description (out of phase) is so deeply ingrained that I should just give up on it. As pointed out, Stereophile uses it as do many manufacturers. I had a Conrad Johnson CD player with a "phase" switch when it was really a polarity switch.

Herman...Agreed that terminology is commonly sloppy. However, "OUT" of phase means a shift of 180 degrees, which is the same thing as a polarity reversal.

No it's not. With a symetrical waveform it is impossible to tell by looking on a scope whether a signal is inverted or 180 degrees out of phase, but musical signals are asymetrical so there is a difference. The usual example is a kick drum that is struck once and then damped. The intial wave that strikes your ear is a compression followed by a rarefaction. If you reverse polarity then it is a rarefaction followed by a compression. This is a big difference. If there was a phase shift then you would still get compression then rarefaction but earlier or later than what it should be.



Waveform A is of equal but opposite polarity to B. They start at the same time but one starts out going positive and the other negative. Waveform C is 1/2 cycle(180 degrees) out of phase with A because it starts 1/2 cycle later. As Eldartford points out, there is no difference between B and C once they get started, but this is because they are symetrical.

Waveform D and E are also equal but opposite polarity while F is phase shifted from D. There is a big difference in E and F whereas B and C appear to be the same. The kick drum (point kd) on waveform D will initially push the speaker cone out while on E it will suck it in.

Some say this all makes no difference in sound, but they are different.

When I said "equal but opposite polarity" I meant equal amplitude but opposite polarity.

If the picture doesn't show up here is the link

[url]http://home.bellsouth.net/p/s/community.dll?ep=334&fileid=1630988&groupid=56202&folderid=203789&curRec=5&folderview=thumbs&ck=[/url]

I see we are still confused, and I don't blame anybody for being that way since it is a bit confusing even without the years of improper use.

AC, which has no + or - poles! Only DC has a + or - polarity. Speakers can have only an absolute phase inversion

This is incorrect. Absolute phase inversion makes no sense. I know what you mean, but it is an incorrect use of the term phase. Phase has to do ONLY with time, and you cannot invert time.

AC does indeed have a polarity at any given given point in time. It may be incorrect to say that a given AC signal is overall positive or negative, but at some points in time it is positive and sometimes it is negative.

A clear example is a balanced system. You have 2 signals. One is the same as what a single ended system would have, and the other is inverted. This second signal is also commonly described as being "180 degrees out of phase" with the other one, but it is not. It's polarity is inverted, not it's phase. In a sense they are mirror images of each other.

When one is going more positive the other is going more negative.
If one has a value at a given point in time of +2 volts and headed more negative, the other one will be -2 volts and headed more positive. As an aside, I see this as a major problem with balanced systems. They must take 2 signals of equal amplitude but opposite polarity and amplify them through 2 different chains of amplifiers with the exact same gain and phase shift in both chains.

A phase shift occurs when different frequency ranges are shifted [delayed] by milliseconds

This is correct. Speaking to Eldartford's earlier point about the phase shift in crossovers being inconsequential, I disagree. At the -3dB (half power) point of a first order filter the phase shift is 45 degrees. This is a significant amount, especially if the fundamental frequency from an instrument falls in the passband and the first harmonic falls outside.

I thought Who was on second.

Eldartford, perhaps you are correct about mic placement, but if you are listening to a live kick drum you will surely be out in front of it unless you are the drummer and the sequence will always be one way or the other, and if you reverse it when playing it back it will sound different.

so that sine waves are back in "phase" if you will pardon the term.

I know what you mean, in and out of phase just seems to sound right, and any use of the term polarity with a modifier seems to sound clunky and incorrect.

Both Hi and Lo signals are shifted 45 degrees at X/O, so the woofer/tweeter discrepancy is 90 degrees (for first order).

I think we are talking about 2 different things here. My point was that all musical instruments produce harmonics in addition to the fundamental tone. So if the fundamental falls inside the passband it will not be phase shifted and if a harmonic falls outside the passband it will be, or vice versa. I think this phase shift in the harmonic structure will be audible. I haven't conducted any experiments to confirm this hypothesis.